Refrigerating apparatus with motor driven centrifugal compressor



May 28, 1957 MOODY 2,793,506

A. M. G. REFRIGERATING APPARATUS WITH MOTOR DRIVEN CENTRIF'UGAL COMPRESSOR Filed March 28, 1955 IN VEN TOR. ARTHUR M. G. MOODY MMTW ATTORNEYS United States Patent REFRIGERATING APPARATUS WITH MOTOR DRIVEN CENTRIFUGAL COMPRESSOR Arthur M. G. Moody, La Crosse, Wis., assignor to The Trane Company, La Crosse, Wis., a corporation of Wisconsin This invention relates to refrigerating apparatus of the type including a motor-compressor assembly, and particularly to apparatus in which a motor and a multi-stage compressor are housed in a sealed unit.

It is an object of this invention to provide means for cooling the motor using the refrigerant of the apparatus as a heat exchange medium.

It is another Object of the invention to provide circulation of refrigerant gas from the condenser to the motor casing, thence over the rotor and stator of the motor, and thence to the cross-over pipe between the first and second stage of the compressor.

It is another object of the invention to provide passageways in the motor casing to conduct refrigerant gas in two streams to the ends of the motor to flow first over the bearings and with each stream then separating into two streams one of which flows over the stator winding and the other of which flows through the gap and outwardly through passageways in the stator.

Other objects and advantages of the invention will appear as the specification proceeds to describe the invention with reference to the accompanying drawings; in which- Figure 1 is a partly diagrammatic view of the refrigeration apparatus of my invention.

Figure 2 is a cross-sectional view of the motor-compressor assembly taken on an axial plane.

Referring now to Figure 1, an electric motor has at one end a first compressor stage 12 and at the other end a second compressor stage 14. A cross-over pipe 16 conducts gas from the discharge of the first stage to the inlet of the second stage 14. The gas discharged from the second stage 14 flows through a pipe 18 to a condenser 20. The condenser 20 may be of the shell-and-tube type in which cooling water flows through the tubing 22 and the refrigerant is in the shell outside the tubes. Refrigerant liquid condensed in condenser 20 flows by gravity through pipe 23 to a float chamber 24. Float 26 in fioat chamber 24 opens and closes to control the flow of refrigerant liquid to an evaporator 28 which is also of the shell-and-tube type in which the secondary refrigerant liquid such as water or brine flows through the tubing 30 and the refrigerant is in the shell outside the tubing 30. The secondary refrigerant liquid circulates between the evaporator 28 and the cooling load served by the refrigeration apparatus to transfer heat from the load to the evaporator 28. In removing heat from the secondary refrigerant, the refrigerant in the evaporator 28 boils forming gas which passes through the liquid eliminator 32 and thence into the suction pipe 34 to the inlet of the first stage compressor 12.

The motor 10 has a fiuid tight casing 35 secured in fluid tight relationship to compressor housings 12 and 14. A motor frame 38 is supported in said fluid tight casing 35 by a pair of rings 40 and 41 which divide the annular space between motor frame 38 and said fluid tight casing 35 into a central chamber 42 and end chambers 44 and 46. Motor frame 38 has bearings 48 and 50 which rotatably support a shaft 36. Shaft 36 extends 2,793,506 Patented May 28, 1957 at one end into compressor housing 12 and has impeller 52 secured thereto. The other end of shaft 36 extends into housing 14 and has impeller 54 secured thereto. A stator 56 is secured to the motor frame 36. Stator 56 has the usual windings 58. A plurality of radial passageways 60 extend through the stator 56. A rotor 62 is mounted on shaft 36 to rotate therewith. Rotor 62 rotates within stator 56 and has an outside diameter slightly less than the inside diameter of the stator 56 to provide a gap between the rotor 62 and stator 56. Refrigerant gas flows from the condenser 20 through a pipe 64 into branch pipes and 72 which in turn conduct the gas to the end chambers 44 and 46 respectively.

After the gas has traversed its path through the motor 10, as will be described in detail below, it flows from the motor 10 through pipe 74 which conducts the gas to the cross-over pipe 16. After entering the pipe 16, this gas flows with the gas discharged from the first stage 12 and enters the second stage 14.

The fiow of gas through pipe 64 may be manually controlled by valve 76. If desired valve 76 may be of the thermostatic type in which a temperature sensing bulb is mounted in the gas stream leaving the motor 10.

The gas, having entered the motor 10 through pipes 70 and 72, flows to end chambers 44 and 46 from which it is conducted by shrouds 67 and 68 into an annular stream surrounding the shaft 36. On leaving the shrouds 67 and 68 part of each stream fiows over the winding 58 and into the central chamber 42 and part of each stream flows into the gap between the rotor 62 and stator 56 and then outwardly through the radial passageways 60 in the stator 56 and into the central chamber 42. Central chamber 42 thus collects the gas flowing over the windings 58 and the gas flowing from the radial passageways 60 and conducts the gas to the pipe 74.

It is thus seen that the gas space above the tubes in the condenser provides a dependable source of gas for motor cooling. Since the condenser is at a pressure substantially equal to the discharge pressure of the second stage 14 and since the pressure in the cross-over pipe 16 is substantially equal to the discharge pressure of the first stage 12, there is sufiicient pressure difference to cause a considerable flow of cooling gas through the motor.

The gas entering the cross-over pipe 16 from the motor 10 through pipe 74 is superheated because it has removed heat from the motor. This superheated gas mixe with the gas in the cross-over pipe 16 and minimizes the danger of condensation of liquid in the second stage of the compressor.

The additional gas passing through the second stage 14 permits a more efiicient second stage design by reason of the fact that the passageways in the impeller can be made slightly wider.

While the apparatus disclosed and described herein constitutes a preferred form of the invention, yet it will be understood that the apparatus is capable of alteration without departing from the scope or spirit of the invention, and that all modifications that fall within the scope of the appended claims are intended to be included herein.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a two stage compressor for circulating refrigerant through said evaporator and condenser, a cross-over conduit for conducting refrigerant from the first stage of the compressor to the second stage of the compressor, a motor for driving said compressor, a fluid tight casing enclosing said motor, said fluid tight casing being in fluid tight engagement with said compressor, a first conduit connected to said condenser and to said fluid tight casing for conducting refrigerant gas from said condenser to said fluid tight casing, a second conduit, connected to said fluid tight casing and to said cross-over conduit for conducting refrigerant gas from said fluid tight casingto said cross-over conduit whereby refrigerant gas flows through said fluid tightcasing to remove heat from the motor.

2. In refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a pipe for conducting refrigerant from said condenser to said evaporator, a Centrifugal compressor having a first compressor stage and a second compressor stage, said first compressor stage being connected to receive refrigerant from said evaporator, 'a crossover conduit for conducting refrigerant from .said first compressor stage to the inlet of said second compressor stage, a pipe for conducting refrigerantfrom said second compressor stage to said condenser, a motor casing in fluid tight engagement with said centrifugal compressor, a motor frame in said motor casing, annular rings between said motorframe-and said motor casing to support said motor frame in said motor casing, said annular rings being arranged to divide the annular space between said motor frameand said motor easing into a central chamber and two end chambers, a stator mounted in said motor frame opposite said central portion, said stator having radial passageways extending therethrough,passageways in said motor frame from said end chambers to the inner ends of said radial passageways, bearings in each end of the motor frame, a shaft and rotor assembly rotatably mounted in said bearings, said shaft and rotor assembly extending into said centrifugal compressor, an impeller in each compressor stage, said impellers being secured to said shaft and rotor assembly, conduit means connected to said condenser and said end chambers for conducting refrigerant from said condenser to said end .chambers, conduit means connected to said central chamberand said cross-over conduit for conducting refrigerant from said central chamber to said cross-over conduit whereby refrigerant is caused to flow from said end chambers through the passageways in said motor frame and then through the radial passageways in the stator to remove heat from the motor.

3. In refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a pipe for conducting refrigerant from said condenser to said evaporator, a first stage centrifugal compressorhaving ,an inlet connected to receive refrigerant from said evaporator, a second stage centrifugal compressor, a cross-over conduit for conducting refrigerant from said first stage centrifugal compressor to the inlet or said second stage centrifugal compressor, a pipe for conducting refrigerant from said second stage centrifugal compressor to said condenser, a motor casing in fluid tight engagement at one end with said first stage centrifugal compressor and at its other end with said second stage centrifugal compressor, a motor frame in said annular motor casing, annular rings between said motor frame and said motor casing to support said motor frame in said motor casing, said annular rings being arranged to divide the annular space between said motor frame and said motor easing into a central chamber and two end chambers, a stator mounted in said motor frame opposite said central portion, said stator having radial passageways extending therethrough, passageways in said motor frame from said endchambers to the inner ends of said radial passageways, bearings in each end of the motor frame, a shaft and rotor assembly rotatably mounted in said bearings, said shaft and rotor assembly having one end extending into said-first stage centrifugal compressor, an impeller secured to said one end of said shaft and rotor assembly, said'shaft and rotor assembly having its'other end extending-into said second stage centrifugal compressor, an impeller secured to said other end of said shaft and rotor assembly, conduit means connected to saidcondenser and said end chambers for conducting refrigerant from,,said condenser to said end chambers, conduit means connected tosaid central chamber and said cross-over conduit for conducting refrigerant from said central chamber to said cross-over conduit whereby refrigerant ,is caused to .flow from said end chambers through the passageways in saidimotor frame and then through the radial passageways in the stator toremove heat from the motor.

4. In refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a pipefor conducting refrigerant from said condenser to said evaporator, a first compressor stage, a second compressor stage, said first compressor stage being connected to receive refrig rant from said evaporator, a cross-over conduit, for conducting refrigerant from said first compressor stage to the inlet of said second compressor stage, a discharge pipe'for conducting refrigerant from said second compressor stage to said condenser, a motor casing in fluid sealing relationship with said compressor stages, a motor frame in said motor casing, hearings in each end of the motor'frame, a shaft and rotor assembly rotatably mounted in said bearings, said shaft and rotor assembly extending into said com pressor stages, an impeller in each of said compressor stages, said impellers being secured to said shaft and rotor assembly, a first conduit connected to said condenser and to said. motor casing for conducting refrigerant from said condenser to said motor casing, a second conduit connected to said motor casing and to said cross-over conduit for conducting refrigerant from said motor casing to said cross-over conduit whereby refrigerant is caused to flowfrom .said condenser to said motor casing and thence to said cross-over conduit to remove heat from the motor casing.

A-ndresen Dec. 6, 1932 Jones Mar. '24, 1942 

